This proposal is to request support for a Keystone Symposia meeting entitled ?The[unreadable] Macrophage: Homeostasis, Immunoregulation and Disease?, which will be held in[unreadable] Copper Mountain, Colorado from April 11-16, 2007. Macrophage-like cells are present[unreadable] in essentially all metazoans. Although often dismissed merely as scavengers, recent[unreadable] genetic, molecular, cellular, and in vivo insights into macrophage biology have focused[unreadable] mechanistic attention on their prodigiously varied roles: as sensors, effectors and[unreadable] regulators of innate immunity; as links between innate and adaptive immunity; as cells[unreadable] central to tissue development and homeostasis; as targets of diverse pathogens; and as[unreadable] cells integral to the pathogenesis of a variety of infectious and non-infectious diseases.[unreadable] Investigation into this profusion of roles has revealed startling conservation of underlying[unreadable] molecular themes and mechanisms, a growing understanding that forms the basis for[unreadable] the organization of this meeting. A special focus of the meeting will be on areas of[unreadable] macrophage biology that are usually neglected, including macrophage differentiation and[unreadable] heterogeneity, and their trophic and developmental roles. The meeting is intended to[unreadable] provide a state-of-the-art overview of macrophage biology, to highlight the translational[unreadable] implications of this work, to provide scientific "cross-fertilization" across different model[unreadable] systems, topics and levels of investigation, and to help define the most important[unreadable] questions to be addressed next in the field.